1. Field of the Invention
The present invention relates to a sound effect adding device which is capable of adding a plurality of sound effects to an input audio signal using a DSP (digital signal processor).
2. Description of the Prior Art
There have been available sound effect adding devices, for example, as disclosed in Japanese First (unexamined) Patent Publication No. 58-50595, wherein a plurality of sound effects are added in a time-division manner using one DSP.
In the foregoing conventional structure, a program corresponding to a sound effect to be added is transferred, per sound effect, to a DSP from a main arithmetic circuit, such as a CPU. Further, since the program is transferred in serial through handshake, the transfer rate is low resulting in a prolonged transfer time. Owing to association with other controls in the device, if the transfer rate is so low, the number of addable sound effects is limited, thereby leading to a poor musical expression.
Further, in the foregoing conventional structure, every time a change in sound effect occurs, a preprocessing, such as a corresponding clearing operation, is performed in a data storage section of the DSP and a corresponding program is transferred to the DSP from the CPU so that the program Is entirely switched to another. This may lead to no outputs of audio signal, an output of queer audio signal or an unstable temporary operation of the DSP during transfer of the program. For avoiding this, Japanese First (unexamined) Patent Publication No. 1-198796 discloses a structure, wherein a circuit bypassing a DSP and a cross-fade circuit are provided so as to cross-fade outputs from the bypassing circuit and the DSP, thereby stabilizing the operation of the DSP even if subjected to a change In sound effect. However, in this conventional structure, an additional discrete part, that is, the cross-fade circuit, is required so that reduction in size of the device and in number of the production steps can not be achieved.